1. Field of Invention
The present invention relates to a light emitting diode structure. More particularly, the present invention relates to a fixing structure of a light emitting diode and a method to assemble thereof.
2. Description of Related Art
The manufacturing technology of light emitting diodes is getting advanced recently, so that the light emitting efficiency for light emitting diodes is accordingly improved. The application of light emitting diode is based on its good characters, such as low operating temperature and low power assumption, etc. Therefore, the light emitting diode is getting more used in the light emitting field. For example, the light emitting diode is introduced to manufacture flashlights or automobile headlights.
The normal LED (Light Emitting Diode) structure consists of the die that is attached to the leadframe with an electrically conductive glue. Gold wire is used to connect the metal contact on the top of the LED die to the adjacent pin. Finally, the epoxy package is molded around the leadframe. Pins set of the leadframe extends outside the LED package. The pins can be inserted into holes in a circuit board, and be fixed on the circuit board by welding. The temperature for welding can be up to hundreds of Celsius degrees, which may be conducted to LED die and make the die burn down.
A prior structure and method of fixing a LED package on a circuit board without welding is provided. Referring to FIG. 1, it illustrates a prior structure and method for fixing a LED package on a transferring board without welding. A LED package 10 includes a conductive leadframe 20. The conductive leadframe 20 has fixing holes 30. Corresponding to the locations of the fixing holes 30, holes 50 are formed by protruding from the bottom surface to the upper surface of a transferring board 40. After the holes 50 are formed, a fixing plate 60 is naturally formed from the protruding part of the holes 50. Referring to FIG. 2, it illustrates a prior structure of a LED package fixed on a transferring board without welding according to FIG. 1. The fixing plate 60 passes through the fixing holes 30, and the fixing plate 60 is bended inside out by using proper tools to fix the LED package 10 with the conductive leadframe 20 on the transferring board 40. The transferring board 40 can be used as a circuit board to transmit current to LED die and a media for heat-dissipation at the same time.
The prior structure and method for fixing a LED package on a transferring board can prevent high temperature which is generated by welding from the assembly processes. However, it is not easy to form a uniform fixing plate 60 by protruding out from the holes 50. Furthermore, the length of the fixing plate 60 is limited by the diameter of the holes 50, which is generally equal to the radii of the fixing holes 30. Referring to FIG. 3, it illustrates a prior structure and method for a fixing plate passing through a fixing hole. The included angle ⊖ between the fixing plate 60 and the transferring board 40 herein is larger than 90 degrees, so that the fixing plate 60 can pass through the fixing hole 30 easily. However, the included angle ⊖ would make it difficult to bend the fixing plate 60 inside out for the following bending process. On the contrary, the fixing plate 60 with the included angle ⊖ would be bended inwards, it accordingly reduce the efficiency for fixing the LED package 10 and the conductive leadframe 20 on the transferring board 40. Thus, for normally fixing the LED package 10 and the conductive leadframe 20 on the transferring board 40, the included angle ⊖ between the fixing plate 60 and the fixing holes 30 should be less than 90 degrees. That is, the fixing plate 60 should be bended inside out. However, it will make the fixing plate 60 passing through the fixing holes 30 difficulty. Therefore, after the fixing plate 60 passing through the fixing holes 30, it needs another process to deal with the included angle ⊖ between the fixing plate 60 and the transferring board 400. It's really a dilemma.
However, one more process will result in increasing cost and decreasing yield rate, even downgrading manufacture automation process. It is not the manufacturers wanted. Thus, it is very important to provide a simple and non-welding structure and method for fixing the LED package and the conductive leadframe on the transferring board.